It is generally agreed that using lethal or otherwise serious force in self-defense is justified only when three conditions are satisfied: first, there are some grounds for the defender to give priority to his own interests over those of the attacker (whether because the attacker has lost the protection of his right to life, for example, or because of the defender’s prerogative to prefer himself to others); second, the harm used is proportionate to the threat thereby averted; third, the harm (...) is necessary to avert that threat. The first and second conditions have been exhaustively discussed, but the third has been oddly neglected. Meanwhile a prominent school of thought has arisen, in the ethics of war, which seeks to ground the justification of killing in war in principles of individual self-defense. They too have failed to offer any substantive analysis of necessity, while at the same time appealing to it when it suits them to do so. In this paper, I attempt a detailed analysis of the necessity constraint on defensive force, and explore the implications of that analysis for the attempt to transpose principles of individual self-defense into the context of warfare. (shrink)

Over the past 20 years, there has been a huge amount of work on which things you can kill in self‐defense and why. This paper surveys that work.

The surge in threats aided by or carried out through cyberspace has placed significant pressure on the intelligence community to adapt or leave itself open to attack. Indeed, many in both political and intelligence circles argue for access to ever greater amounts of cyber information in order to catch potential threats before they become real. By collecting all our digital information, the intelligence community argues that it is not only able to detail what people have done or are currently doing (...) but also predict what their next move might be. However, the ethical implications are unclear and the backlash following Edward Snowden’s revelations have shown that such activities are not without controversy. This leaves the debate stuck between the important, ethical role that intelligence can play and the potential for its unrestrained use to cause undue harm. This paper will resolve this by giving greater detail to cyber-intelligence practices, highlighting the different levels of harm that the various intelligence operations can cause. The essence of this paper is not that cyber-intelligence should be banned outright, but that it can be justified given the necessary circumstances. Therefore, the paper will develop a specialised set of Just Cyber-Intelligence Principles, built on the just war tradition, to outline if and when such activities are justified. (shrink)

The principle of non-combatant immunity protects non-combatants against intentional attacks in war. It is the most widely endorsed and deeply held moral constraint on the conduct of war. And yet it is difficult to justify. Recent developments in just war theory have undermined the canonical argument in its favour – Michael Walzer's, in Just and Unjust Wars. Some now deny that non-combatant immunity has principled foundations, arguing instead that it is entirely explained by a different principle: that of necessity. In (...) war, as in ordinary life, harms to others can be justified only if they are necessary. Attacking non-combatants, the argument goes, is never necessary, so never justified. Although often repeated, this argument has never been explored in depth. In this article, I evaluate the necessity-based argument for non-combatant immunity, drawing together theoretical analysis and empirical research on anti-civilian tactics in interstate warfare, counterinsurgency, and terrorism. (shrink)